BSB, a joint-venture between Bharti and SoftBank, said Thursday that it has made a fresh investment of $7 million in Hike, its free messaging app.

Hike acquired 5 million users in four months, after its launch on December 12 last year. This makes 'hike' one of the fastest growing free mobile apps globally. Hike competes with other free instant messaging apps like Whatsapp, Facebook Messenger and BlackBerry Messenger.

Hike offers seamless integration between instant messaging and standard text messaging (SMS) which is extremely effective in a market like India where 90% of the 900 million strong mobile population uses feature phones.

About 60% of hike's user base comes from India and the rest global led by Middle East and Europe. hike is available on iOS, Android, Windows Phone & S40 platforms. The company also recently launched hike for Blackberry beta.

"The response for hike has been phenomenal especially in such a competitive market. This new round of investment is an endorsement of the great work put in by our product teams," said Mike Kayamori, Director, BSB.

Kavin Bharti Mittal, head of product and strategy, BSB, said that an upgrade of the app which has been announced will offer new features for users.

The Hike 2.0 update features Status Updates with Moods that lets users post updates about what they are up to or what they are thinking in real-time to their close friends only. Users can curate a 'Circle of Friends' in the app to whom the update goes out to.